Commonly assigned U.S. Pat. No. 4,893,307, issued Jan. 9, 1990, "Method and Apparatus for Linking SNA Terminals to an SNA Host Over a Packet Switched Communications Network", D. B. McKay, R. M. Morten and M. P. Marsili, describes an architectural model of the Department of Defense (DoD) protocol suite. Referring to FIG. 1 the architecture is said to be similar to, but not identical with, the International Standards Organization (ISO) Open Systems Interconnection (OSI) architecture.
A Defense Data Network (DDN) standard establishes criteria for an Internet Protocol (IP) which supports the interconnection of communication LANs. It introduces the Internet Protocol's role and purpose, defines the services provided to users, and specifies the mechanisms needed to support those services. The standard also defines the services required of the lower protocol layer, describes the upper and lower interfaces, and outlines the execution environment services need for implementation.
A Transmission Control Protocol (TCP) is a transport protocol providing connection-oriented, end-to-end reliable data transmission in packet-switched computer LANs and internetworks.
The Internet Protocol (IP) and the Transmission Control Protocol (TCP) are mandatory for use in all DoD packet switching networks which connect or have the potential for utilizing connectivity across network or subnetwork boundaries. Network elements, such as hosts, front-ends, gateways, etc., within such networks which are to be used for internetting must implement TCP/IP.
The Internet Protocol is designed to interconnect packet-switched communication LANs to form an internetwork. The IP transmits blocks of data, called internet datagrams, from sources to destinations throughout the internet. Sources and destinations are hosts located on either the same subnetwork or connected LANs. The IP is purposely limited in scope to provide the basic functions necessary to deliver a block of data. Each internet datagram is an independent entity unrelated to any other internet datagrams. The IP does not create connections or logical circuits and has no mechanisms to promote data reliability, flow control, sequencing, or other services commonly found in virtual circuit protocols.
The DDN standard specifies a host IP. As defined in the DoD architectural mode, the Internet Protocol resides in the internetwork layer. Thus, the IP provides services to transport layer protocols and relies on the services of the lower network protocol. In each gateway, a system interconnecting two or more LANs, an IP resides above two or more LANs protocol entities. Gateways implement the internet protocol to forward datagrams between networks. Gateways also implement the Gateway to Gateway Protocol (GGP) to coordinate signalling and other internet control information.
The Internet protocols were originally developed with an assumption that users, each of which is assigned a unique Internet address, would be connected to the network at fixed locations. However, for portable and handheld computers the movement, or migration, of users about the network is typically the rule rather than the exception. As a result, a problem is created in that the implicit design assumptions of the Internet protocol are violated by this type of usage.
Other patents of interest include the following. In U.S Pat. No. 4,914,652, issued Apr. 3, 1990, Nguyen discloses a method for managing data transmissions in a single network, but not the routing and delivery of data between networks. In U.S. Pat. No. 4,750,109, issued Jun. 7, 1988, Kits teaches methods for allocating communication channels. In U.S. Pat. No. 4,706,081, issued Nov. 10, 1987, Hart et al. teach the merging of physically separate networks into a single logical network at a level below the addressing considerations required to affect the Internet protocols. In U.S. Pat. No. 4,644,461, issued Feb. 17, 1987, Jennings discloses a computer architecture including cross-bar and queue structures for routing tokens within the computer.
In commonly assigned U.S. Pat. No. 4,809,257, issued Feb. 28, 1989, entitled "Hierarchical Distributed Infrared Communication System" Gantenbein et al. disclose the integration of workstations into an IR network. FIG. 1D shows a system that includes a gateway 23 to another network such as a ring or a bus local area network, or to a cable-bound subnetwork.
Other patents of interest include the following. In U.S. Pat. No. 4,807,222, issued Feb. 21, 1989, N. Amitay discloses a wireless network using intelligent interfaces for each wired network connection. The interface is to a token bus network.
In U.S. Pat. No. 4,665,519, issued May 12, 1987, T. L. Kirchner et al. disclose the use of VHF FM radio as a means of connecting computers and computer peripherals. This patent describes the implementation of an asynchronous access, token based protocol. In International Patent W088/07794, published Oct. 6, 1988, G. Vacon discloses the use of a wireless microwave bridge between two networks utilizing a CSMA/CD protocol.
In IBM Technical Disclosure Bulletin Vol. 24 No. 8, 1982 F. Gfeller describes general control principles of an infrared wireless communication network incorporating multiple base stations and multiple mobile computers. Transmission occurs over the wireless IR medium using different frequencies for the uplink and the downlink.
What is not taught by this prior art, and what is thus an object of the invention to provide, is method and apparatus for coupling wireless migrating users to a network operating in accordance with the TCP/IP type-protocol.